/*
 * The MIT License
 *
 * Copyright (c) 2011 Takahiro Hashimoto
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package jp.a840.websocket.handshake;

import jp.a840.websocket.BufferManager;
import jp.a840.websocket.HttpHeader;
import jp.a840.websocket.exception.ErrorCode;
import jp.a840.websocket.exception.WebSocketException;
import jp.a840.websocket.util.StringUtil;

import java.nio.ByteBuffer;
import java.util.EnumMap;
import java.util.EnumSet;

/**
 * Processing WebSocket Handshake
 *
 * <pre>
 * Sample (Draft06)
 * client => server
 * GET /chat HTTP/1.1
 * Host: server.example.com
 * Upgrade: websocket
 * Connection: Upgrade
 * Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
 * Sec-WebSocket-Origin: http://example.com
 * Sec-WebSocket-Protocol: chat, superchat
 * Sec-WebSocket-Version:6
 *
 * server => client
 * HTTP/1.1 101 Switching Protocols
 * Upgrade: websocket
 * Connection: Upgrade
 * Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
 * Sec-WebSocket-Protocol: chat
 * </pre>
 *
 * @author Takahiro Hashimoto
 */
public abstract class Handshake {

    /**
     * The response status.
     */
    private int responseStatus;

    /**
     * The response header map.
     */
    private HttpResponseHeaderParser httpResponseHeaderParser;

    /**
     * The Enum State.
     *
     * @author Takahiro Hashimoto
     */
    enum State {

        /**
         * The INIT.
         */
        INIT,
        /**
         * The METHOD.
         */
        METHOD,
        /**
         * The HEADER.
         */
        HEADER,
        /**
         * The BODY.
         */
        BODY,
        /**
         * The DONE.
         */
        DONE;

        /**
         * The state map.
         */
        private static EnumMap<State, EnumSet<State>> stateMap = new EnumMap<State, EnumSet<State>>(State.class);

        static {
            stateMap.put(INIT, EnumSet.of(State.METHOD));
            stateMap.put(METHOD, EnumSet.of(State.HEADER));
            stateMap.put(HEADER, EnumSet.of(State.BODY, State.DONE));
            stateMap.put(BODY, EnumSet.of(State.DONE));
            stateMap.put(DONE, EnumSet.of(State.METHOD));
        }

        /**
         * Can transition to.
         *
         * @param state the state
         * @return true, if successful
         */
        boolean canTransitionTo(State state) {
            EnumSet<State> set = stateMap.get(this);
            if (set == null) return false;
            return set.contains(state);
        }
    }

    /**
     * Transition to.
     *
     * @param to the to
     * @return the state
     */
    protected State transitionTo(State to) {
        if (state.canTransitionTo(to)) {
            State old = state;
            state = to;
            return old;
        } else {
            throw new IllegalStateException("Couldn't transtion from " + state + " to " + to);
        }
    }

    /**
     * The state.
     */
    private volatile State state = State.INIT;

    /**
     * State.
     *
     * @return the state
     */
    protected State state() {
        return state;
    }

    /**
     * The buffer manager.
     */
    protected BufferManager bufferManager = new BufferManager();

    /**
     * Handshake response.
     *
     * @param downloadBuffer the download buffer
     * @return true, if successful
     * @throws WebSocketException the web socket exception
     */
    final public boolean handshakeResponse(ByteBuffer downloadBuffer) throws WebSocketException {
        ByteBuffer buffer = null;
        try {
            if (state == State.INIT || state == State.DONE) {
                transitionTo(State.METHOD);
                responseStatus = -1;
                httpResponseHeaderParser = new HttpResponseHeaderParser();
                bufferManager.init();
                buffer = downloadBuffer;
            } else {
                buffer = bufferManager.getBuffer(downloadBuffer);
            }

            if (state == State.METHOD || state == State.HEADER) {
                int position = buffer.position();
                if (!parseHandshakeResponseHeader(buffer)) {
                    buffer.position(position);
                    bufferManager.storeFragmentBuffer(buffer);
                    return false;
                }
                transitionTo(State.BODY);
            }

            if (state == State.BODY) {
                int position = buffer.position();
                if (!parseHandshakeResponseBody(buffer)) {
                    buffer.position(position);
                    bufferManager.storeFragmentBuffer(buffer);
                    return false;
                }
            }

            return done();
        } finally {
            if (buffer != null && buffer != downloadBuffer) {
                downloadBuffer.position(downloadBuffer.limit() - buffer.remaining());
            }
        }
    }

    /**
     * Done.
     *
     * @return true, if successful
     */
    protected boolean done() {
        transitionTo(State.DONE);
        return true;
    }

    /**
     * Checks if is done.
     *
     * @return true, if is done
     */
    public boolean isDone() {
        return state == State.DONE;
    }

    /**
     * Parses the handshake response contents.
     *
     * @param buffer the buffer
     * @return true, if successful
     * @throws WebSocketException the web socket exception
     */
    protected boolean parseHandshakeResponseBody(ByteBuffer buffer) throws WebSocketException {
        return true;
    }

    /**
     * Parses the handshake response header.
     *
     * @param buffer the buffer
     * @return true, if successful
     * @throws WebSocketException the web socket exception
     */
    protected boolean parseHandshakeResponseHeader(ByteBuffer buffer)
            throws WebSocketException {

        if (state == State.METHOD) {
            // METHOD
            // HTTP/1.1 101 Switching Protocols
            String line = StringUtil.readLine(buffer);
            if (line == null) {
                return false;
            }
            if (!line.startsWith("HTTP/1.1")) {
                throw new WebSocketException(ErrorCode.E3101, line);
            }
            responseStatus = Integer.valueOf(line.substring(9, 12));
            if (responseStatus != 101) {
                throw new WebSocketException(ErrorCode.E3102, line);
            }
            transitionTo(State.HEADER);
        }

        if (state == State.HEADER) {
            httpResponseHeaderParser.parse(buffer);
            return httpResponseHeaderParser.isCompleted();
        }

        return true;
    }

    /**
     * Creates the handshake request.
     *
     * @return the byte buffer
     * @throws WebSocketException the web socket exception
     */
    abstract public ByteBuffer createHandshakeRequest()
            throws WebSocketException;

    /**
     * Gets the response status.
     *
     * @return the response status
     */
    public int getResponseStatus() {
        return responseStatus;
    }

    /**
     * Gets the response header map.
     *
     * @return the response header map
     */
    public HttpHeader getResponseHeader() {
        return httpResponseHeaderParser.getResponseHeader();
    }
}
